Methods and systems for improving power delivery and signaling in stacked semiconductor devices

ABSTRACT

Semiconductor die assemblies including stacked semiconductor dies having parallel plate capacitors formed between adjacent pairs of semiconductor dies in the stack, and associated systems and methods, are disclosed herein. In one embodiment, a semiconductor die assembly includes a first semiconductor die and a second semiconductor die stacked over the first semiconductor die. The first semiconductor die includes an upper surface having a first capacitor plate formed thereon, and the second semiconductor die includes a lower surface facing the upper surface of the first semiconductor die and having a second capacitor plate formed thereon. A dielectric material is formed at least partially between the first and second capacitor plates. The first capacitor plate, second capacitor plate, and dielectric material together form a capacitor that stores charge locally within the stack, and that can be accessed by the first and/or second semiconductor dies.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/684,703, filed Aug. 23, 2017, which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

The present technology generally relates to stacked semiconductordevices. Several embodiments of the present technology are related toimproving power delivery to stacked semiconductor devices by formingcapacitors between adjacent semiconductor dies in the stack.

BACKGROUND

Microelectronic devices, such as memory devices, microprocessors, andlight emitting diodes, typically include one or more semiconductor diesmounted to a substrate and encased in a protective covering. Thesemiconductor dies include functional features, such as memory cells,processor circuits, interconnecting circuitry, etc. Semiconductor diemanufacturers are under increasing pressure to reduce the volumeoccupied by semiconductor dies and yet increase the capacity and/orspeed of the resulting encapsulated assemblies. To meet these demands,semiconductor die manufacturers often stack multiple semiconductor diesvertically on top of each other to increase the capacity or performanceof a microelectronic device within the limited volume on the circuitboard or other element to which the semiconductor dies are mounted. Insome semiconductor die stacks, the semiconductor dies are electricallyinterconnected using through silicon vias (TSVs). The TSVs enable thesemiconductor dies to be stacked close to each other such that adjacentsemiconductor dies are spaced apart from each other by only relativelysmall vertical distances. This, along with the relatively low inductanceof the TSVs, enables higher data transfer rates. Also, since the diesare stacked vertically, the total footprint of the stack corresponds tothe footprint of the largest die in the stack.

However, one concern with semiconductor die stacks is power delivery.For example, the current draw from semiconductor dies in the stack canbe significant when the semiconductor dies are performing high poweroperations, which can result in poor power delivery to, for example, theuppermost semiconductor dies in the stack. Conventional methods forimproving power delivery in semiconductor die stacks include increasingthe TSV count of each semiconductor die in the stack to reduce theresistance of the power network. However, increasing the TSV count ofthe semiconductor dies often requires increasing the size of thesemiconductor dies. Accordingly, there remains a need in the art formethods and systems for improving power delivery in semiconductor diestacks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a semiconductor die assembly inaccordance with an embodiment of the present technology.

FIGS. 2A and 2B are a top plan view and bottom plan view, respectively,of a semiconductor die configured in accordance with an embodiment ofthe present technology.

FIGS. 3A and 3B are a top plan view and bottom plan view, respectively,of a semiconductor die configured in accordance with another embodimentof the present technology.

FIGS. 4A-4C are cross-sectional views illustrating a semiconductor dieat various stages of manufacturing in accordance with an embodiment ofthe present technology.

FIG. 5 is a schematic view of a system that includes a semiconductor dieassembly configured in accordance with embodiments of the presenttechnology.

DETAILED DESCRIPTION

Specific details of several embodiments of semiconductor dies andsemiconductor die assembles are described below. In several of theembodiments described below, a semiconductor die assembly includes astack of semiconductor dies having a capacitor formed between eachadjacent pair of semiconductor dies in the stack. In some embodiments,the capacitors are parallel plate capacitors that include (a) an upperplate formed on a lower surface of an upper one of each adjacent pair ofsemiconductor dies, (b) a lower plate formed on an upper surface of alower one of each adjacent pair, and (c) a dielectric material betweenthe upper and lower plates. The parallel plate capacitors can storecharge locally within the stack of semiconductor dies. When anindividual semiconductor die has a spike in its demand for power, theindividual semiconductor die can pull power from one or more of theparallel plate capacitors to address that demand. Moreover, in certainembodiments, the plates of the parallel plate capacitors can be formedas part of existing metallization processes for forming interconnectsbetween the stacked semiconductor dies, without adding much cost orcomplexity to the manufacturing process.

As used herein, the terms “vertical,” “lateral,” “upper,” and “lower”can refer to relative directions or positions of features in thesemiconductor dies and semiconductor die assemblies described herein, inview of the orientation shown in the Figures. For example, “upper” or“uppermost” can refer to a feature positioned closer to the top of apage than another feature. These terms, however, should be construedbroadly to include semiconductor dies and semiconductor die assemblieshaving other orientations, such as inverted or inclined orientationswhere top/bottom, over/under, above/below, up/down, and left/right canbe interchanged depending on the orientation.

FIG. 1 is a cross-sectional view illustrating a semiconductor dieassembly 100 (“assembly 100”) configured in accordance with anembodiment of the present technology. The assembly 100 includes a stack105 of semiconductor dies 110 carried by a package substrate 120. Thepackage substrate 120 can include an interposer, a printed circuitboard, a dielectric spacer, another semiconductor die (e.g., a logicdie), or another suitable substrate. The package substrate 120 isconnected to electrical connectors 122 (e.g., solder balls) thatelectrically couple the assembly 100 to external circuitry (not shown).In some embodiments, the assembly 100 can include an interposer, anotherlogic die, or other suitable structure between the package substrate 120and a lowermost one of the semiconductor dies 110.

The semiconductor dies 110 can each have integrated circuits orcomponents, data storage elements, processing components, and/or otherfeatures manufactured on semiconductor substrates. For example, thesemiconductor dies 110 can include integrated memory circuitry and/orlogic circuitry, which can include various types of semiconductorcomponents and functional features, such as dynamic random-access memory(DRAM), static random-access memory (SRAM), flash memory, other forms ofintegrated circuit memory, processing circuits, imaging components,and/or other semiconductor features. In some embodiments, thesemiconductor dies 110 can be identical (e.g., memory dies manufacturedto have the same design and specifications), but in other embodimentsthe semiconductor dies 110 can be different from each other (e.g.,different types of memory dies or a combination of controller, logic,and/or memory dies). Further, although the assembly 100 includes foursemiconductors dies 110 stacked on the package substrate 120, in otherembodiments the assembly 100 can include fewer than four semiconductordies (e.g., two dies or three dies) or more than four dies (e.g., fivesdies, six dies, eight dies, twelve dies, sixteen dies, thirty-two dies,etc.).

As further shown in FIG. 1, the semiconductor dies 110 each have anupper surface 113 a and a lower surface 113 b opposite the upper surface113 a (collectively “surfaces 113 a, 113 b”). Some of the semiconductordies 110 can further include a plurality of vias 112 (e.g., throughsilicon vias (TSVs)) extending at least substantially through thesemiconductor dies 110 (e.g., through a semiconductor substratethereof). In some embodiments, each via 112 includes an electricallyconductive material (e.g., copper) that passes completely through anindividual semiconductor die 110, and an electrically insulativematerial surrounding the electrically conductive material toelectrically isolate the via 112 from the remainder of the semiconductordie 110. More particularly, the vias 112 can extend completely throughthe semiconductor dies 110 such that an upper portion of each via 112 isexposed at the upper surface 113 a of an individual semiconductor die110, and a lower portion of the via 112 is exposed at the lower surface113 b of the individual semiconductor die 110. In this manner, the vias112 are configured for mechanical and/or electrical connection to othersemiconductor dies 110 in the 105 and/or to the package substrate 120.As illustrated in the embodiment of FIG. 1, the uppermost semiconductordie 110 in the stack 105 can be provided without vias since electricalconnection through the uppermost semiconductor die 110 (e.g., at theupper surface 113 a of the uppermost semiconductor die 110) may not benecessary. In other embodiments, the uppermost semiconductor die 110 canalso include a plurality of vias 112, for example, to permit electricalcoupling of the uppermost semiconductor die 110 to other circuitry(e.g., additional semiconductor dies, higher level circuitry, etc.) atthe upper surface 113 a of the uppermost semiconductor die 110. In stillother embodiments, the semiconductor dies 110 can be electricallycoupled together without the use of TSVs, using other interconnectmethods well known to those skilled in the art (including, e.g.,shingled wirebonds, face-to-face interconnects, etc.).

The assembly 100 further includes a plurality of electrically conductiveinterconnects 130 extending between and electrically coupling adjacentsemiconductor dies 110 in the stack 105. The interconnects 130 can eachinclude an upper metallization feature 132, a lower metallizationfeature 134, and an electrically conductive element 136 coupling theupper and lower metallization features 132, 134 (collectively“metallization features 132, 134”). The electrically conductive elements136 can comprise a solder material, for example tin-silver, indium, oranother suitable solder material for forming an electrical andmechanical connection between the metallization features 132, 134 onadjacent semiconductor dies 110. In other embodiments, the electricallyconductive elements 136 can be made of other suitable materials and/orhave different structures (e.g., copper pillars, bump-on nitridestructures, etc.).

The metallization features 132, 134 can be, in general, any suitableunder-bump metal (UBM) structure as known in the art, and areelectrically coupled to corresponding ones of the vias 112 of thesemiconductor dies 110. The upper metallization features 132 are formedon the lower surface 113 b of an upper semiconductor die 110 of a pairof adjacent semiconductor dies 110 in the stack 105. Similarly, thelower metallization features 134 are formed on the upper surface 113 aof a lower semiconductor die 110 of the pair of adjacent semiconductordies. More particularly, as shown in FIG. 1, the upper metallizationfeatures 132 can be formed over the lower portions of the vias 112exposed at the lower surface 113 b of the upper semiconductor die 110 ofthe pair of adjacent semiconductor dies. Likewise, the lowermetallization features 134 can be formed over the upper portions of thevias 112 exposed at the upper surface 113 a of the lower semiconductordie 110 of the pair of adjacent semiconductor dies. Accordingly, theinterconnects 130 (i.e., the upper metallization features 132,electrically conductive elements, and lower metallization features 134)can be axially aligned with and electrically couple a pair of vias 112in the pair of adjacent semiconductor dies. However, in otherembodiments, the interconnects 130 need not be axially aligned with thevias 112. For example, a redistribution layer (RDL) or otherelectrically conductive structure on the lower and/or uppersemiconductor dies 110 in the pair of adjacent semiconductor dies canprovide a different alignment and coupling between the vias 112 of theadjacent semiconductor dies and the metallization features 132, 134.

The metallization features 132, 134 can comprise any one or combinationof suitable conductive materials such as, for example, copper, nickel,gold, silicon, tungsten, etc., and can have a thickness (e.g., height)of between about 1-100 microns (e.g., less than about 10 microns).Moreover, the shape and dimension of the metallization features 132, 134can vary. For example, in some embodiments, the metallization features132, 134 have a substantially cylindrical cross-sectional shape and formpillar-like structures. In other embodiments, the metallization features132, 134 can have other cross-sectional shapes such as rectangular,regular polygonal, irregular polygonal, elliptical, etc.

The assembly 100 further includes a plurality of upper capacitor plates142 and a plurality of lower capacitor plates 144 (collectively“capacitor plates 142, 144”). Each upper capacitor plate 142 is formedon the lower surface 113 b of an upper semiconductor die 110 of a pairof adjacent semiconductor dies 110 in the stack 105, and each lowercapacitor plate 144 is formed on the upper surface 113 a of a lowersemiconductor die 110 of the pair of adjacent semiconductor dies. Asillustrated in the embodiment of FIG. 1, each upper capacitor plate 142faces a corresponding lower capacitor plate 144 and is at leastpartially aligned with the corresponding lower capacitor plate 144. Forexample, as shown in FIG. 1, each upper capacitor plate 142 issuperimposed over the corresponding lower capacitor plate 144 on theadjacent lower semiconductor die 110 (e.g., the capacitor plates 142,144 are substantially reflectively symmetric about a plane extendingbetween the adjacent semiconductor dies). At least one of the capacitorplates 142, 144 is electrically coupled to a power supply while theother is electrically coupled to ground. For example (as shown in FIGS.2A and 2B), the capacitor plates 142, 144 can each be electricallycoupled to one or more of the interconnects 130, providing a power orground signal, via conductive traces formed on the surfaces 113 a, 113 bof the semiconductor dies 110. In other embodiments, the capacitorplates 142, 144 can be electrically coupled to the power supply orground using other suitable electrical connectors such as wirebonds.Accordingly, a voltage difference can be provided between the opposingcapacitor plates 142, 144 formed between each pair of adjacentsemiconductor dies 110 in the stack 105.

As described in further detail below with reference to FIGS. 4A-4C, thecapacitor plates 142, 144 can be formed as an extension of themetallization process used to form the metallization features 132, 134(e.g., at the same processing stage and/or simultaneously). Accordingly,because they can be formed from the same process, at least some of thecharacteristics of the metallization features 132, 134 and capacitorplates 142, 144 can be the same or substantially similar. For example,the metallization features 132, 134 can have the same or a substantiallysimilar thickness as the capacitor plates 142, 144, respectively.Similarly, the metallization features 132, 134 can comprise the samematerial (e.g., copper, nickel, gold, silicon, tungsten, etc.) as thecapacitor plates 142, 144.

The assembly 100 can further include a dielectric material 150 depositedor otherwise formed around and/or between the semiconductor dies 110,the interconnects 130, and the capacitor plates 142, 144 to electricallyisolate these components and/or to enhance the mechanical connectionbetween the semiconductor dies 110 in the stack 105. The dielectricmaterial 150 can be a non-conductive epoxy paste, a capillary underfill,a non-conductive film, a molded underfill, and/or include other suitableelectrically-insulative materials.

Together, each pair of opposing capacitor plates 142, 144 and thedielectric material 150 therebetween form a mid-stack capacitor (e.g., aparallel plate capacitor) that stores charge within the stack 105. Thecharge stored on each parallel plate capacitor is proportional to thecapacitance (C) of the capacitor, C=k ϵ₀ A/d, where “k” is the relativepermittivity of the dielectric material between the plates, “ϵ₀” is thevacuum permittivity, “A” is the area of the capacitor plates, and “d” isthe spacing between the capacitor plates. In some embodiments, themid-stack capacitors formed in the assembly 100 each have a capacitanceof 10's to 100's of picoFarads (e.g., more than about 100 picoFarads).Moreover, because the capacitance—and therefore the charge stored by thecapacitor—depends inversely on the distance between the capacitor plates142, 144, the capacitance can be increased as the vertical distance(e.g., the spacing) between the semiconductor dies 110 in the stack 105is reduced. The spacing between the semiconductor dies 110 in the stack105 depends largely on the size of the interconnects 130. Therefore, astechnology progresses to reduce the size of the interconnects 130 and tothereby reduce the overall height of the assembly 100, the capacitanceof the mid-stack capacitors described herein can be correspondinglyincreased. Furthermore, in some embodiments, the dielectric material 150can be selected based on its dielectric qualities (e.g., its relativepermittivity or other characteristics) so as to increase the capacitanceof the mid-stack capacitors.

In general, each mid-stack capacitor in the stack 105 adds capacitanceto the power network of the stack 105 that can be drawn on by thesemiconductor dies 110 when needed. For example, when an individualsemiconductor die 110 in the stack 105 has a spike in its need for power(e.g., when the individual semiconductor die 110 performs a powerintensive operation such as initiating an access, read operation, etc.)the individual semiconductor die 110 can draw some of the power it needsfrom one or more of the mid-stack capacitors. The mid-stack capacitorsoffer a more localized power source than an external power supply, whosepower must be routed through the package substrate 120 and up throughthe vias 112 and interconnects 130. Accordingly, the mid-stackcapacitors can quickly address some of the short term power demands ofthe semiconductor dies 110, which the power supply may be slow inresponding to depending on the power needs of other semiconductor dies110 in the stack 105 (e.g., lower semiconductor dies in the stack).Conventional methods to improve the power delivery of a semiconductordie stack increase the TSV count of each semiconductor die in the stackto include more power and ground connections to thereby reduce theresistance of the power network. However, increasing the TSV count ofthe semiconductor dies requires increasing the size of the semiconductordies. The present technology advantageously increases the capacitance ofthe power network in the assembly 100 such that the assembly 100 canbetter meet the power demands of the semiconductor dies 110 in the stack105, without increasing the TSV count and/or size of the semiconductordies 110.

Moreover, adding capacitance to the power network can improve the signalintegrity of signals transmitted through the stack 105 on one or more ofthe vias 112 and/or the performance of the semiconductor dies 110. Forexample, the mid-stack capacitors can act as decoupling capacitors toshunt noise that may otherwise be carried through the stack 105 (e.g.,voltage spikes or ground bounce caused by other dies in the stack) andthat may hinder the performance of the semiconductor dies 110. Themid-stack capacitors may also help address problems with inductiveringing (e.g., ringing due to package self-inductance in memorydevices). For examples, the mid-stack capacitors can help minimize theinductive path for the power supply and ground connections to therebyimprove the performance of the semiconductor dies 110.

As shown in FIG. 1, a mid-stack capacitor is formed between each pair ofadjacent semiconductor dies 110 in the stack 105. The mid-stackcapacitors can be electrically coupled in parallel or in series, or insome combination thereof. However, in some embodiments, the stack 105may be provided with only one mid-stack capacitor formed between asingle pair of adjacent semiconductor dies 110, or with any other numberof mid-stack capacitors. In some embodiments, an additional capacitorcan be formed between the package substrate 120 and the lowermostsemiconductor die 110 in the stack 105 by providing (a) a lowercapacitor plate 144 on the package substrate 120, (b) a correspondingupper capacitor plate 142 on the lower surface 113 b of the lowermostsemiconductor die 110, and (c) a dielectric material (e.g., thedielectric material 150) therebetween. Similarly, in some embodiments, acapacitor can be formed between the upper surface 113 a of the uppermostsemiconductor die 110 in the stack 105 and any external componentsconnected thereto.

FIGS. 2A and 2B are a top and bottom plan view, respectively, of one ofthe semiconductor dies 110 of the assembly 100 shown in FIG. 1 havingmetallization features and a capacitor plate on each of the surfaces 113a, 113 b of the semiconductor die 110, in accordance with embodiments ofpresent technology. The illustrated semiconductor die 110 can be one ofthe semiconductor dies 110 in the middle of the stack 105 (e.g., havingan adjacent semiconductor die 110 both above and below), as thelowermost and topmost semiconductor dies 110 in the stack 105 may beformed without a capacitor plate and/or metallization features on theirlower and upper surfaces 113 b, 113 a, respectively (as illustrated inFIG. 1).

More particularly, FIG. 2A illustrates the upper surface 113 a of thesemiconductor die 110 having one or more peripheral regions 216 (e.g.,laterally outboard regions) and a central region 218. The lowermetallization features 134 are formed on the peripheral region 216, andthe lower capacitor plate 144 is formed on the central region 218 of theupper surface 113 a. The lower capacitor plate 144 can be electricallycoupled to one or more of the lower metallization features 134 viaconductive traces 238 (shown individually as conductive traces 238 a and238 b). For example, as illustrated in the embodiment of FIG. 2A, thelower capacitor plate 144 can be electrically coupled to a first lowermetallization feature 134 a via the conductive trace 238 a and to asecond lower metallization feature 134 b via the conductive trace 238 b.The first and second lower metallization features 134 a, 134 b can beelectrically coupled to either ground or to a power supply. In someembodiments, the conductive traces 238 are formed as part of the samemetallization process as the lower metallization features 134 and lowercapacitor plate 144.

FIG. 2B illustrates the lower surface 113 b of the semiconductor die 110having one or more peripheral regions 226 (e.g., laterally outboardregions) and a central region 228. The upper metallization features 132are formed on the peripheral region 226, and the upper capacitor plate142 is formed on the central region 228 of the lower surface 113 b. Theupper capacitor plate 142 can be electrically coupled to one or more ofthe upper metallization features 132 via conductive traces 248 (shownindividually as conductive traces 248 a and 248 b). For example, asillustrated in the embodiment of FIG. 2B, the upper capacitor plate 142can be electrically coupled to a first upper metallization feature 132 avia the conductive trace 248 a and to a second upper metallizationfeature 132 b via the conductive trace 248 b. The first and second uppermetallization features 132 a, 132 b can be electrically coupled toeither ground or to a power supply. In some embodiments, the conductivetraces 248 are formed as part of the same metallization process as theupper metallization features 132 and upper capacitor plate 142.

In some embodiments, the capacitor plates 142, 144 can be electricallycoupled to the same vias (FIG. 1) of the semiconductor die 110.Accordingly, the capacitor plates 142, 144 can either be bothelectrically coupled to ground or both electrically coupled to the powersupply. In such embodiments, each alternating semiconductor die 110 inthe stack 105 can be provided with the same configuration of capacitorplates 142, 144 such that a voltage difference exists between opposingcapacitor plates 142, 144 formed between adjacent pairs of semiconductordies 110 in the stack 105. However, in other embodiments, the capacitorplates 142, 144 on the semiconductor die 110 can be electrically coupledto different (e.g., separate) ones of the vias 112 such that one of thecapacitor plates 142, 144 is electrically coupled to ground, while theother is electrically coupled to the power supply. For example, in suchembodiments, each upper capacitor plate 142 in the stack 105 can beelectrically coupled to the power supply while each lower capacitorplate 144 is electrically coupled to ground.

Referring to both FIGS. 2A and 2B together, the capacitor plates 142,144 can be formed to fill a substantial area of the surfaces 113 b, 113a, respectively, that are not otherwise occupied by the metallizationfeatures 132, 134. For example, as illustrated in both FIGS. 2A and 2B,the semiconductor die 110 can have metallization features 132, 134arranged in rows at the peripheral regions 216, 226 of the surfaces 113a, 113 b. By forming the capacitor plates 142, 144 on the centralregions 218, 228 and to have a rectangular cross section (e.g., arectangular planform shape), the capacitor plates 142, 144 can occupy asubstantial area of the surfaces 113 a, 113 b that is not occupied bythe metallization features 132, 134 (whose position may be limited to alocation of the vias 112). For example, in some embodiments, thecapacitor plates 142, 144 can cover an area greater than about 25% ofthe surface area of the surfaces 113 a, 113 b of the semiconductor die110, respectively. In some embodiments, the capacitor plates 142, 144can cover an area greater than about 50% of the surface area of thesurfaces 113 a, 113 b. In still other embodiments, the capacitor plates142, 144 can cover an area greater than about 75% of the surface area ofthe surfaces 113 a, 113 b. However, the coverage of the capacitor plates142, 144 is not limited and the capacitor plates 142, 144 can cover anysuitable portion of the surfaces 113 a, 113 b. Moreover, in certainembodiments, the metallization features 132, 134 may be formed on adifferent region of the semiconductor die 110, and can have differentarrangements. In such embodiments, the size, shape, and positioning ofthe capacitor plates can be selected to match the layout of themetallization features 132, 134.

For example, FIGS. 3A and 3B are a top and bottom plan view,respectively, of one of the semiconductor dies 110 of the assembly 100having a different arrangement of metallization features and capacitorplates on the surfaces 113 a, 113 b of the semiconductor die 110, inaccordance with another embodiment of the present technology. Referringto both FIGS. 3A and 3B together, the metallization features 132, 134are arranged in rows that are evenly spaced along the surfaces 113 b,113 a, respectively. The metallization features 132, 134 can be arrangedin this manner to, for example, match the arrangement of the vias (e.g.,the vias 112) of the semiconductor die 110. As shown in FIG. 3A, a lowercapacitor plate 344 is formed on the upper surface 113 a of thesemiconductor die 110 and electrically coupled to one or more of thelower metallization features 134 (e.g., corresponding to power orground) via conductive traces 338. Similarly, as shown in FIG. 3B, anupper capacitor plate 342 is formed on the lower surface 113 b of thesemiconductor die 110 and electrically coupled to one or more of theupper metallization features 132 via conductive traces 348 (e.g.,corresponding to power or ground). In some embodiments, both the upperand lower capacitor plates 342, 344 are electrically coupled to the samevias 112 (FIG. 1) of the semiconductor die 110 (e.g., such that bothplates are grounded or both plates are connected to a power supply),while in other embodiments, the upper and lower capacitor plates 342,344 are electrically coupled to different ones of the vias 112 (e.g.,such that one of the plates is grounded while the other is connected tothe power supply). Moreover, both the upper and lower capacitor plates342, 344 have a generally rectilinear shape and are formed on asubstantial portion of the open surface area around the metallizationfeatures 132, 134. Such an arrangement can generally allow for the upperand lower capacitor plates 342, 344 to have the greatest area given thelayout of the metallization features 132, 134.

In general, the size, shape, and positioning of the capacitor platesdescribed herein can be selected to maximize or nearly maximize the areaof the capacitor plates, so as to increase the capacitance of mid-stackcapacitors formed in a die stack. More particularly, each capacitorplate can be formed on the open surface area of a semiconductor die thatwould otherwise be unoccupied by metallization features. Thus, thecapacitor plates described herein are adaptable to the specificconfiguration of the semiconductor dies on which they are formed (e.g.,to the arrangement of vias, metallization features, and/or otherfeatures), while also adding little or no additional overhead to the dieassembly (e.g., not increasing the planform size or thickness of the dieassembly).

Moreover, each semiconductor die can include a single capacitor plate ona surface thereof, as described in connection with several embodimentsabove, or more than one capacitor plate on a surface thereof. Forexample, a semiconductor die as described herein can include multiplediscrete capacitor plates to match the room available on the surface ofthe semiconductor die given the existing metallization structures. Thediscrete capacitor plates may be electrically coupled (e.g., viaconductive traces) or electrically isolated. In some embodiments,adjacent semiconductor dies may each have multiple discrete capacitorplates on facing surfaces thereof so as to form multiple discreteparallel plate capacitors between the adjacent semiconductor dies. Themultiple parallel plate capacitors can operate independent of eachother, or may be connected in parallel, in series, etc.

FIGS. 4A-4C are cross-sectional views illustrating various stages in amethod of manufacturing a semiconductor die having metallizationfeatures and capacitor plates formed thereon, in accordance withembodiments of the present technology. In the embodiment illustrated inFIGS. 4A-4C, a plurality of semiconductor dies 110 can be formed atdiscrete areas of a substrate assembly 400 (e.g., a semiconductor waferor panel). The substrate assembly 400 includes a semiconductor material460 and a dielectric material 462 on an upper side of the semiconductormaterial 460. Although only a single semiconductor die 110 isillustrated in FIGS. 4A-4C, in practice the substrate assembly 400typically has several hundred or even over 1,000 individualsemiconductor dies.

Referring to FIG. 4A, at this stage of processing, the vias 112 havebeen formed in the semiconductor material 460. As will be readilyunderstood by those skilled in the art, the vias 112 can be made byetching a high-aspect-ratio hole into the semiconductor material 460 andfilling it with one or more materials in one or more deposition and/orplating steps. For example, in the embodiment shown in FIG. 4A, the vias112 include a dielectric liner 464 and a conductive plug 466 within thedielectric liner 464. As further shown in FIG. 4A, upper portions of thevias 112 are exposed at the upper surface 113 a of the semiconductor die110.

FIG. 4B illustrates the substrate assembly 400 after forming the lowermetallization features 134 over the upper portions of the vias 112, andafter forming the lower capacitor plate 144 on the upper surface 113 aof the semiconductor die 110. Notably, the lower capacitor plate 144 canbe formed as an extension of the metallization process used to form thelower metallization features 134. The metallization process can be anysuitable metallization process (e.g., a front-side metallization orunder-bump metallization process) known in the art. In some embodiments,for example, the lower metallization features 134 are formed bydepositing a copper seed structure onto the dielectric material 462 andthe upper portions of the vias 112, forming a mask on the copper seedstructure having openings aligned with the upper portions of the vias112, plating copper onto the seed structure, and then plating one ormore other materials over the copper to form the lower metallizationfeatures 134. The lower capacitor plate 144 can be formed as part ofsuch a process by adjusting the mask pattern to include one or moreopenings corresponding to a desired shape, position, and size of thelower capacitor plate 144 and any trace(s) (e.g., the traces 238 in FIG.2A) connecting the lower capacitor plate 144 to one or more of the lowermetallization features 134. In some embodiments, after forming the lowermetallization features 134 and lower capacitor plate 144 (and, in someembodiments, the electrically conductive elements 136), the mask isremoved and the exposed portions of the seed structure are removed usinga suitable wet etch to isolate the lower metallization features 134 andthe lower capacitor plate 144.

FIG. 4C illustrates the substrate assembly 400 after (a) thinning thesemiconductor material 460 to expose the lower surface 113 b of thesemiconductor die 110 and lower portions of the vias 112 (e.g., usingback grinding, dry etching processes, chemical etching processes,chemical mechanical polishing (CMP), etc.); (b) forming a dielectricmaterial 468 on a lower side of the semiconductor material 460; (c)forming the upper metallization features 132 over the lower portions ofthe vias 112; and (d) forming the upper capacitor plate 142 on the lowersurface 113 b of the semiconductor die 110. The upper capacitor plate142 can be formed as an extension of the metallization process used toform the upper metallization features 132, which can be any suitableprocess known in the art (e.g., a back-side metallization or under-bumpmetallization process). In some embodiments, the metallization processused to from the lower metallization features 134 and lower capacitorplate 144 can be the same metallization process used to form the uppermetallization features 132 and upper capacitor plate 142. In otherembodiments, the processes may be different. For example, at least someof the stages illustrated in FIGS. 4A-4C need not be carried out for theuppermost and lowermost dies in the stack, which can be formed withoutcapacitor plates and/or metallization features on at least one surface.Once processing of the substrate assembly 400 is complete, thesemiconductor dies 110 can be singulated from the substrate assembly 400and incorporated into a die assembly (e.g., the assembly 100 shown inFIG. 1).

Notably, the capacitor plates 142, 144 can be formed without addingsignificant additional costs or complexity to existing methods forforming the metallization features 132, 134, since the capacitor plates142, 144 can be formed as an extension of those methods. Likewise,conductive traces (e.g., the traces 238/248 and 338/348 shown in FIGS.2A-3B) can also be easily formed as part of the same methods, forelectrically coupling the capacitor plates 142, 144 to correspondingmetallization features 132, 134 to provide a suitable voltage differencebetween the plates.

Any one of the semiconductor devices having the features described abovewith reference to FIGS. 1-4C can be incorporated into any of a myriad oflarger and/or more complex systems, a representative example of which issystem 500 shown schematically in FIG. 5. The system 500 can include aprocessor 502, a memory 504 (e.g., SRAM, DRAM, flash, and/or othermemory devices), input/output devices 505, and/or other subsystems orcomponents 508. The semiconductor die assembly 100 and semiconductordies 110 described above with reference to FIGS. 1-4C can be included inany of the elements shown in FIG. 5. The resulting system 500 can beconfigured to perform any of a wide variety of suitable computing,processing, storage, sensing, imaging, and/or other functions.Accordingly, representative examples of the system 500 include, withoutlimitation, computers and/or other data processors, such as desktopcomputers, laptop computers, Internet appliances, hand-held devices(e.g., palm-top computers, wearable computers, cellular or mobilephones, personal digital assistants, music players, etc.), tablets,multi-processor systems, processor-based or programmable consumerelectronics, network computers, and minicomputers. Additionalrepresentative examples of the system 500 include lights, cameras,vehicles, etc. With regard to these and other example, the system 500can be housed in a single unit or distributed over multipleinterconnected units, e.g., through a communication network. Thecomponents of the system 500 can accordingly include local and/or remotememory storage devices and any of a wide variety of suitablecomputer-readable media.

From the foregoing, it will be appreciated that specific embodiments ofthe technology have been described herein for purposes of illustration,but that various modifications may be made without deviating from thedisclosure. Accordingly, the invention is not limited except as by theappended claims. Furthermore, certain aspects of the new technologydescribed in the context of particular embodiments may also be combinedor eliminated in other embodiments. Moreover, although advantagesassociated with certain embodiments of the new technology have beendescribed in the context of those embodiments, other embodiments mayalso exhibit such advantages and not all embodiments need necessarilyexhibit such advantages to fall within the scope of the technology.Accordingly, the disclosure and associated technology can encompassother embodiments not expressly shown or described herein.

I claim:
 1. A semiconductor die assembly, comprising: a firstsemiconductor die having a lower surface and an upper surface oppositethe lower surface; a second semiconductor die having a lower surface andan upper surface opposite the lower surface, the second semiconductordie stacked over the first semiconductor die such that the lower surfaceof the second semiconductor die faces the upper surface of the firstsemiconductor die; a first metal structure on the upper surface of thefirst semiconductor die; a second metal structure on the lower surfaceof the second semiconductor die; and a dielectric material between thefirst and second metal structures, wherein the dielectric material andthe first and second metal structures together form a capacitor.
 2. Thesemiconductor die assembly of claim 1 wherein the first metal structurehas a surface area greater than about 25% of the area of the uppersurface of the first semiconductor die.
 3. The semiconductor dieassembly of claim 1 wherein the first metal structure has a surface areagreater than about 50% of the area of the upper surface of the firstsemiconductor die.
 4. The semiconductor die assembly of claim 1 whereinthe first metal structure has a surface area greater than about 75% ofthe area of the upper surface of the first semiconductor die.
 5. Thesemiconductor die assembly of claim 1, further comprising: a pluralityof first metallization features on the upper surface of the firstsemiconductor die, wherein the first metallization features areelectrically coupled to interconnects extending at least partiallythrough the first semiconductor die, and wherein the first metalstructure is electrically coupled to at least one of the firstmetallization features; and a plurality of second metallization featureson the lower surface of the second semiconductor die, wherein the secondmetallization features are electrically coupled to interconnectsextending at least partially through the second semiconductor die, andwherein the second metal structure is electrically coupled to at leastone of the second metallization features.
 6. The semiconductor dieassembly of claim 5 wherein the upper surface of the first semiconductordie includes a first portion and a second portion, wherein the firstmetallization features are formed on the first portion of the uppersurface of the first semiconductor die, and wherein the first metalstructure is formed on substantially all of the second portion of theupper surface of the first semiconductor die.
 7. The semiconductor dieassembly of claim 6 wherein the lower surface of the secondsemiconductor die includes a first portion and a second portion, whereinthe second metallization features are formed on the first portion of thelower surface of the second semiconductor die, and wherein the secondmetal structure is formed on substantially all of the second portion ofthe lower surface of the second semiconductor die.
 8. The semiconductordie assembly of claim 7 wherein the first metal structure and the secondmetal structure have rectangular planform shapes that are reflectivelysymmetric about a plane extending therebetween.
 9. The semiconductor dieassembly of claim 1 wherein the dielectric material is selected from thegroup consisting of a non-conductive epoxy paste, a capillary underfill,a non-conductive film, and a molded underfill.
 10. A method, comprising:forming a plurality of first metallization features on a first surfaceof a semiconductor die, the first metallization features electricallycoupled to through silicon vias (TSVs) extending through thesemiconductor die; while forming the first metallization features,forming a first capacitor plate on the first surface, the firstcapacitor plate electrically coupled to at least one of the firstmetallization features; forming a plurality of second metallizationfeatures on a second surface of the semiconductor die, the secondmetallization features electrically coupled to the TSVs; and whileforming the second metallization features, forming a second capacitorplate on the second surface, the second capacitor plate electricallycoupled to at least one of the second metallization features.
 11. Themethod of claim 10 wherein the semiconductor die is a firstsemiconductor die, and wherein the method further comprises: providing asecond semiconductor die having a third capacitor plate formed on asurface of the second semiconductor die; stacking the firstsemiconductor die over the second semiconductor such that at least aportion of the second capacitor plate is over the third capacitor plate;and depositing a dielectric material at least partially between thesecond capacitor plate and the third capacitor plate.
 12. The method ofclaim 11 wherein the method further comprises: forming a plurality ofthird metallization features on the surface of the second semiconductordie, the third metallization features electrically coupled to throughsilicon vias (TSVs) extending through the second semiconductor die; andwhile forming the third metallization features, forming the thirdcapacitor plate on the surface of the third semiconductor die, the thirdcapacitor plate electrically coupled to at least one of the thirdmetallization features.
 13. The method of claim 10 wherein the methodfurther comprises, before forming the second metallization features,thinning the semiconductor die to expose end portions of the TSVs at thesecond surface of the semiconductor die.
 14. The method of claim 10wherein forming the first metallization features includes forming thefirst metallization features on a laterally outboard region of the firstsurface, and wherein forming the second metallization features includesforming the second metallization features on a laterally outboard regionof the second surface.
 15. The method of claim 10 wherein forming thefirst capacitor plate includes forming the first capacitor plate onsubstantially all of a laterally inboard region of the first surface,and wherein forming the second capacitor plate includes forming thesecond capacitor plate on substantially all of a laterally inboardregion of the second surface.
 16. The method of claim 10 wherein thedielectric material is an underfill material.
 17. A method of operatinga semiconductor die assembly including a stack of semiconductor dies,the method comprising: storing charge in at least one mid-stackcapacitor formed between an adjacent pair of semiconductor dies in thestack, the mid-stack capacitor including an upper plate formed on alower surface of an upper one of the adjacent pair of semiconductordies, a lower plate formed on an upper surface of a lower one of theadjacent pair of semiconductor dies, and a dielectric material betweenthe upper and lower plates; and providing power from the mid-stackcapacitor to at least one of the semiconductor dies.
 18. The method ofclaim 17 wherein providing power from the mid-stack capacitor includesproviding power to the at least one of the semiconductor dies when theat least one of the semiconductor dies performs a power intensiveoperation.
 19. The method of claim 18 wherein the power intensiveoperation is at least one of initiating an access or a read operation.20. The method of claim 17 wherein the method further comprisessupplying power to the semiconductor dies from an external power supply,and wherein the mid-stack capacitor provides a more proximate source ofpower than the external power supply to the at least one of thesemiconductor dies.